SOLO floats ("sounding oceanographic Lagrangian observers"),
invented by Russ Davis of the Scripps Institution of Oceanography, can
be programmed to descend as deep as 2,000 meters to measure temperature
and salinity, then resurface to send their data to satellites overhead.

Seeing the potential of SOLOs as robotic carbon observers, Jim
Bishop and his colleagues devised instruments that SOLOs could use
to measure organic carbon particles like plankton and inorganic particles
like calcite, the most common carbon mineral in seawater.

By installing advanced two-way telemetry, Bishop's
group made it possible for SOLOs to transmit more data at a faster rate.

Researchers were also able to reprogram diving schedules remotely.

Since wind and waves often make it impossible to contact communications
satellites, the floats can store several days' worth of data and play
it back later. "SOLO floats are designed to operate in all weather
conditions," says Bishop. "They fly in the oceans as balloons
fly in the air, for seasons at a time."

A much tougher test came in the winter of 2002, when four SOLOs were
deployed during
the SOFeX experiment to test the "iron hypothesis" in the
Southern Ocean, the stormiest place on the planet. The result: unexpected
discoveries and major savings of costly ship time, through pinpoint tracking
of patches of fertilized plankton growth.